Process of and apparatus for converting heavy mineral oils into lowerboiling products



v July 1, 1930. w. G LEAMON PROCESS OF AND APPARATUS FOR CONVERTINGHEAVY MINERAL OILS INTO LCWER BOILING PRODUCTS Filed June 26, 1925 www.

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llllllfl Patented July 1930 PATENT ori-uca WILLIAM e. Laarzen, orNEWARK, omo' PROCESS @E .APPARATUS FOR CONVERTING- HEAVY MINERAL OILSNTO LOWER- BOILING PRODUCTS Application led June 26, 1925. Serial No.39,743.

This invention relates to improvements in processes of and apparatus forconverting heavy mineral oils into lower-boiling products; and itrelates more particularly to the treatment of relatively heavy mineraloils of the petroleum type for the manufacture of lower-boiling productstherefrom, such as motor `fuel and the like.

In an advantageous practical embodiment, the process of the inventioninvolves a procedure wherein the mineral oil to be converted or crackedis first heated to a temperature below that normally eEective forcracking but suiciently high to vaporize a substantial ortion of the oilwhile leaving a higher-boiling portion, including tarry constituents,unvaporized and commingled with the vapors,l the unvaporized liquidparticles are then separated in any sultable manner from the vaporswhile avoiding extensivalowering of the temperature of the vapors, andthe vapors alone are then brought to a temperature that is amply high toeect cracking, but so irap-v idly as to avoid such extensive cracking atthis stage as would cause excessive deposition of carbon, whereupon thevapors thus rapidly superheated are directed into a cracking chambermaintained at temperatures somewhat lower but still effective forcracking, the vapors traveling through this cracking chamber slowlyenough to give ample time for eective vapor-phase cracking, and theresultant cracked vapors being then appropriately treated to recovertherefrom a lowerboiling condensate, such as a motor fuel condensate.

ln said process, the initial heating of the oil, and the subsequentrapid superheating of the oil vapors free from liquid, are mostdesirably accomplished in the coils of one or more pipe-coil heaters orstills through which the oil and the oil vapors respectively pass in theform of a rapidly moving stream of relatively small thickness; and thevaporphase cracking chamber or zone, which is most advantageously butnot necessarily provided with a filling of adsorptive contact material,is maintained within the desired range of cracking temperatures by thesuperheat of the hot vapors supplied thereto rather than by externalheating.

A further understanding of the rinciples of the invention can best beobtained through a concrete illustrative embodiment thereof which willnow be described in connection with the accompanying drawings in whichFig. 1 is a more or less diagrammatic or schematic representation, inside elevation, ofvone form of apparatus system that can be used toadvantage in practicing the process .of 'the invention; and

Fig. 2 is a similar view of a part of' the aforesaid system showing are-arrangement of certain of the units.

Referring to the drawings, and at first more particularly to Fig. 1, 10representsa supply tank containing the heavy mineral oil to ecracked orconverted. A topped crude petroleum is an example of a heavy mineral oilthat can be successfully cracked or converted by the present process,but it is to be understood that many other kinds of mineral oil andresidua ma be used. From this tank the oil is drawn y pump 11 and umpedthrough line 12, either directly to pipe still 13,.or, and moreadvantageously, through heat exchan ers 14 and 15 where the oil ispreheated by t e hot vapors coming from the ycracking zone to bereferred to presently. ln

a typical instance, the pressure at the pump discharge may be in theneighborhood of 100 pounds, and ordinarily there is a drop of around 10to 15 pounds in going through the heat exchanger system..

The preheated oil is next conducted into the first or lower coil 16 ofthe pipe still, the upper or superheater coil being indicated at 1 Inthis lower coil the oil 1s heated to a temperature ordinarilyrangingfrom. about 360 to 425 C., the exact temperature most desirableto employ being dependent somewhat upon the particular oil beingtreated. A temperature within this range, while insulciently high toeffect extensive cracking, is nevertheless high enough to vaporizepractically all that portion of the oil which it is desired to permit toenter the cracking or converting zone. The mixture of vapors and liquidparticles of unvaporized heavy constituents commingled therewith leavethe initial heating coil 16 and are subjected to suitable treatment formechanical separation of and vapor stream is greatly reduced upon itsdischarge into the separating means, however, and that accordingly asubstantial time factor is introduced, vaporization that was incipientin the heater coil 16 has an opportunity to o to completion in saidseparating means. uch further vaporization as may thus occur absorbsheat and hence there is some drop in temperature of the`oil vapors inundergoing separation which may amount to from 10 to 30 degreescentigrade in typical instances, but this is not an extensive loweringof temperature within the intended meaning of this expression as hereinemployed. The pressure in the separating means 1s not substantiallylower than that under which the mixture of liquid and vapor leaves coil16.

In the present example, the separating means comprise aplurality ofserially arranged units, of which the first is an upright separator 19of the vertical cylindrical type, optionally provided in its upper partwith bafiies 20. lIn this separator chamber the unvaporized constituentsof the oil, including tarry matter, drop out in liquid form and collect1n the lower part of the separator from which they may be Withdrawn fromtime to time or continuously through valved discharge outlet 21. Inpractice,l the liquid thus separated is usually allowed to collect inthe separator until it reaches, say, the level indicated at 22, when itis then withdrawn.

l The hot oil vapors, substantially free of liquid, leave the separatorthrough exit pipe 23 and, in this particular instance, pass then througha second separator unit consisting of a centrifugal separator device ofany known or suitable type, indicated at 24, where any slight residualtraces of tarry or other liquid matter can be removed from the vapors,the liquid matter so separated passing through tar line 25 to the lowerpart of the separator 19, as indicated. Where the vapors leaving thelower coil of the pipe still through line 18 do not carry with them toolarge a proportion of liquid material, it is even feasible to dis ensewith the separator 19 and to rely entirely upon a centrifugal separator,such as that indicated at 24, for removal of unvaporized constituentsfrom the oil vapors. From the separator 24, the mineral oil vapors passthrough vapor line 26 into the ,upper heating coil 17 of the pipe still.This coil is subjects to more intense heat than coil 16, and the oil`vapors in passing at high veloicty through the vapors leaving the coil17 througlh vapor line 27, are at a temperature as hig as is attainablewithout causing coking in coil 17 or line 27. As a rule, it is foundthat this maximum temperature cannot ordinarily much exceed 600o C.without too much cracking and carbon deposition occurring in the heatercoil. By the time the superheated oil va ors arrive at the discharge oroutlet end o the superheater coil 17, they are under much less pressurethan the oil entering the lower or preliminary heater coil 16. Forexample, t e pressure on the oil vapors when they leave the superheatercoil 17 may be only about 10 pounds, this reduction being due in largemeasure to frictional losses incurred in forcing the oil vapors throughthe pipe-coils of the heater.

The superheated vapors leaving the pipe still through line 27 enter thetop of the vapor-phase cracking unit 28 and pass down wardlytherethrough at very'much reduced velocity. This cracker unit is hereshown as of the vertical cylindrical type, roviding in its interior acracking zone. ost desirably this cracking zone contains a mass ofporous adsorptive contact material 28a inert to sulfur, nitrogen andcarbon under the conditions of opeartion, through which vthe oil vaporsare obliged to pass. Pumice in lumps, ranging in size from 5 or 6 inchesin diameter down, constitutes an admirable contact material for thepurposes of the present process. While the use of such a Contactmaterial is to be recommended as giving best results, the invention inits broader phases is to be understood as not restricted to the use ofsuch material. Where the cracking zone is not filled with contactmaterial, the cracking reaction occurs much less rapidly and a largerproportion of fixed gases results.

The cracker unit should be provided with a. heavy lagging of suitableheat insulation in order to cut down heat losses to a minimum. It isadvisable also to similarly lag thel heat exchangers 14, 15, the pipestill 13, and the separators 19 and 24, as well as all the pipingconnections between these parts. Within the cracking zone thetemperature of the oil vapors decreases rapidly at first adjacent thepoint of their entry into said zone. The temperature then decreases moregradually to a minimum at the point where the vapors leave the crackingzone through vapor line 29. Under the operating conditions here assumed,the pressure of the vapors in the cracker may be very slightly aboveatmospheric, 4 or 5 pounds for exam le. The pressure drop between thesuper eater coil outlet and the cracking zone, is thus slight, say 5 or6 pounds, and hence the temperature drop due to expansion of thesuperheated vapors upon entering the cracking zone is minimized. largepart of the decrease in temperature of the vapors as they progressthrough the izing cracking. However, by thoroughly insulating thecracking zone as described, and by operating with small pressure dropbetween the outlet of the heater coil and the cracking zone, thecracking zone may be j maintained at eective operating temperaturesentirely by the superheat of the oilv vapors entering the same andwithout the employment of external heating. This is especiallyadvantageous because, where thev mineral oil vapors are uniformlysuperheated as described to a temperature above that' necessary toeffect cracking, all the dliiicultles incident to external heating'of acracking zone, such as local overheating with attendant carbondeposition and coking, may be wholly avoided; while at the same time, byreason of the uniform heating. conditions to which every portion of thevapor is subjected'in the cracking zone according to the procedureherein-set forth,the results are correspondingly much more dependableand uniform, especially where an adsorptive contact Inaterial -of thecharacter above mentioned is employed in the cracking chamber.Furthermore, the control of temperatures in the cracking zone is thusgreatly simplified because of the fact that it'becomes necessary only toregulate the rate at which thepipe still is fired and the rate at whichoil ispumped through the heating coil or coils thereof.

1n a typical instance, the pipe of the superheater coil 17 may be 2 to 4inches in diameter and 1000 feet in length; while the furnace may be sofired as to give furnace temperatures around the coil near its outletend high enough to ensure heating the oil vapors toA the desired maximumtemperature. Assuming that the vapors are discharged from thesuperheating coil 17 through the outlet of vapor line 27 at 600 C. orsllghtly above, and also assuming that the interior of the verticalcylindrical crackingunit 28 is 10 feet high and 10 feet in diameter,pyrometer observations at about the center of the cracking zone usuallyindicate temperatures ranging from 530 to 550 C., or somewhat higher,under normal operating conditions.; while the temperature of the vaporsjust before theyleave the cracker unit. through vapor line 29 mayA be 20to 30 degrees lower. These figures, as

tially-free of any obstruction, the time of passage of vaporstherethrough should ordinarily be two or three times as long. Thesetimes are to be understood as merely approximate and only generallyillustrative of ne mode of successful operation. f

In general it may be said that around 490 C. is usuallyabout the minimumtemperature at which cracking reactions proceed withsucient rapidity tobe practically useful in carrying-on the present process, and hence itis desirable to so proportion and arrange the apparatus, and to sooperate it, that the temperature of the vapors leaving the cracking zoneis not materially below that point.

n the cracking or converting chamber 28, the oil undergoes a vapor-phasecracking-or splitting operation with production of a large proportion oflower-boiling constituents on the one hand, and formation of a smallamount of heavy liquid products on the other due to re-combination ofcertain of cracked products. Such liquid products may be Withdrawncontinuously or intermittently through valved tar outlet pipe 30. Whileit is in this chamber that the main cracking or conversion of the vaporsoccurs, and while reference has been made to the fact that no extensivecracking of the oil occurs during the brief period of its passagethrough the-pipe still in the preliminary superheating operation, it isto be understood that this statement is relative and is not intendedtoimply that absolutely no cracking whatever may occur in the superheatingcoil of the pipe still, but such cracking as may occur should not be soextensive as to cause substantial deposition of carbon in said coil.

Where the craclmn-g chamber 28 contains` porous adsorptive contactmaterial of the character hereinabove mentioned, substan-J tially noseparation of carbon occurs in the cracking zone and, in particular,none that produces coky deposits and chokes up the converting orcracking zone. ln starting up the plant for the first time, it is foundthat a. veryr thin film-like deposit of carbon is soon formed on thelumps of pumice or other contact material ;`in fact the existence ofthis lmflike deposit on said contact material is apparently highlyadvantageous in the way of assisting and acceleratin the convertingaction, and it is even ossi le that it is an essential factor inattaining thoroughly satisfactory and ecient action of the Contactmaterial. f But, once this film-like deposit is formed, it does not growthicker as time goes on but seems to remain unchanged. At all, events,it is entirely feasible in practice to run the plant continuously forweeks or` even'V months at a time without shutting down to clean out thecracking chamber.

Where the process is carried out without the use of contact material inthe cracking Zone, -Y

some perceptible deposition of` carbon oclof tarry and other heavyproducts is deposited. However, even where contact material is notemployed in the cracking zone,

thev fact that cracking by contact of the oil vapors with directlyheated or superheated surfaces is eliminated eatly reduces the tendencyfor carbon toe deposited either from further cracking of the aforesaidtarry or other heavy products or lfrom excessive crackin of the feed oilvapors. Hence, in thisemodiment of the invention also, much longeroperation can be had without the necessity of shutting down to clean outthan is possible with the externally fired chambers heretofore used invapor-phase crackin Hot cracked vapors leaving the crac chamber throughexit line 29 are conducted through heat exchangers 15 and 14 insuccession where they -give up a part of their heat units to the liquidoil that is being supplied to the ipe still 13, thus serving to preheatsuch oil as already explained. At the same time, the cracked vapors losetheir superheat and some undesirable heavy constituents are liquefiedand separated. The liquid separated in the heat exchangers may bedisposed of in any desired manner, but in the present instance it isconducted by lines 31, 32 and 33 to the storage tank 10 for re-running.

The vapors leaving the last of the series of heat exchangers (which mayof course be more than two in number) pass through vapor line 34 into adephlegmator 35 of any suitable type. Here further relatively highboilinconstituents that it is desirable to exclu e from the motor fuelcondensate sought are separated and are most desirably sent by way oflines 36 and 33 to the supply storage tank 10.

The vapors leaving the dephlegmator pass through line 37 to condenser38, and a crude motor fuel condensate collects in receiver 39, fixedgases passing off through vent pipe 40. A pump 41 may be arran ed towithdraw a part of the crude con ensate from receiver 39 and return thesame through line 42 to the top of the dephlegmator 35 in order tn aideffective functioning of the latter.

The crude motor fuel condensate obtained in receiver 39 as hereinabovedescribed may be further refinedby redistillation or other suitablerefining method to produce a refined gasoline or other motor fuel ofdesired specications. Any residue from redistillation may be sent tostorage tank 10 and worked through the process again. l

Fig. 2 illustrates how the process of the in-l vention may beadvantageously carried out in a manner somewhat different specificallyfrom that described in connection with Fig. 1. In this modified form ofprocedure, the heat exchangers 15 and 14, supplemented by such others inseries therewith as lit may be found desirable to employ in practice,are relied upon to bring the topped crude or other starting material upto a temperature corresponding to that which it attains by passagethroughthe lower coil 16 of the pipe still 13 shown in Fig. 1.Accordingly, the hot oil comin from heat exchanger 15 through line 12,an consisting of a mixture of oil vapors and unvaporized heavy liquidoil, is passed directly into separator unit 19 where the unvaporizedheavy material drops out as liquid, the vapors leaving the top of theseparator and passing by way of vapor line 23, centrifugal separatorunit 24, and line 26, into the pipe still 113 which in this instance maycontain a single continuous coil 117 corresponding in function to thesuperheater coil 17 of Fig. 1. The course ofthe superheated vaporsleaving the pipe still 113 through vapor line 27 is the same as beforedescribed in connection with Fig. 1.

By vaporizing the desired proportion of the oil and dropping out theliquid or unvaporized portion of the vapor-liquid mixture before the oilvapors enter the pipe still, the advantage is gained that only oilvapors, substantially free of liquid oil, are treated in the coil of thepipe still, and hence the danger of carbon deposition in the heater coilis rendered still more remote and the operation of the system as a Wholeis rendered correspondingly simpler and more easily controllable.

Although in the description given hereinabove in explaining theprinciples of the invention the cracking zone is refered to as beingmaintained substantially at or only very slightly above atmosphericpressure, it is to be understood that substantial superatmosphericpressures may be employed in the cracking zone and other parts of thesystem within the scope of the invention.

The terms converting and cracking are used herein interchangeably andeach generic to the other, to designate broadly the molecular changesundergone by mineral oils generally when subjected to heat at aSuffilength of time to cause breaking down, splittin or cleavin of themolecules, with or wit out deposition of carbon and with forciently hightemperature and for a sutlicient p effective cracking temperature whileleaving a high-boiling portion including contained tarr mattersubstantiall in unvaporized con ition but commingle with the vapors,

se aratin out the unva orized ortion, fur- P g P P ther heatmg saidvapors to a temperature in excess of that re uired for effectivecracking but 'so ra idly t at said vapors leave this stage of theprocess largely uncracked, then maintaining said vapors ,in acrackingzone kept at eii'ective cracking temperature substantially only by thesuperheat of said vapors for a period of time long enough toeiectextensive cracking, andv recovering a relativel low-boiling 'condensate'from the crac ed vapors.

- uid, superheatingsaid vapors while they travel at high velocity in astream of small diameter to a temperature above that required forcracking b ut within a period of time so short that they remain largelyun cracked, then reducing the velocity of the vapors and maintainingthem at cracking temlong to e perature substantially only' by thesuperheat of said va ors for a period of time suciently @ect extensivecracking, and recovering a relatively low-boiling condensate from thecracked vapors. 4

3. The process of converting mineral oil into lower-boiling products,which comprises subjecting mineral oil traveling in a stream ofrelatively small thickness to heat at temperatures below crackingtemperatures but suciently high to vaporize a desired portionof said oilwhile leaving heavy constitu ents of the oil as liquid commingled with 50 v ing to occur, and recovering a relatively lowthe vapors, separatingsuch liquid from the vapors, passing said vapors at high velocitythrough a heated coil until they attain a temperature in theneighborhood of 600 C., but

within a period of time so short that nocracking occurs sucient to causesubstantial 1 deposition of carbon, discharging the vapors into acracking chamber wherein the temperature is below 600 C. but ismaintained high enou h for eective cracking substantially only y thesuperheat of said vapors, fallowing said vapors to -travel through saidchamber slowly enough to permit extensive crackboiling condensate fromthe cracked vapors.

4. The process deiined in claim 1, furthercharacterized by the fact thatin said cracking zone the oil vapors pass through a mass 'of porousadsorptive contact material.,

5. The process deiined in claim 2, further characterized by the factthat the cracking ofthe oil vapors 'is effected with the aidof porousadsorptive contact material inert 'to sulfur, nitrogen and carbonunderthe conditions of operation.

6. The process characterized by the 'fact that in traveling through saidcracking chamber, lsaid vapors pass through a mass of lump pumice.

7. A process of oil conversion which includes heating heavy mineral oilto a temperature sufficiently high to vaporize a substantial portionthereof while leaving unvaporized a high-boiling point .portion thereof,including tarry constituents, separating therefrom the vaporizedportion, and subjecting the latter to superheating to a temperatureabove that required for the cracking reaction but within a period oftime so short that no crackin occurs suliicient to cause substantialdeposition of carbon, passing the superheated vapors through a mass ofporous adsorptive material, said vapors belng superheated sufficientlyto maintain by their contained heat the desired cracking reactionof thevapors when passed through said material while maintaining said materialat the required temperature for said reing reaction but within a periodof time so 9short that nocracking occurs sucient to vcause substantialdeposition of carbon, pass ing the superheated vapors into adecomposit1on-chamber wherein said vapors are retained at crackingtemperature for a period of time long enough to eect extensive crack.ing, said vapors being heated sufficiently to maintain by theircontained heat the desired cracking reaction of the vapors While in saidchamber, and separating a condensate of the motor fuel type from theresultant vapors.

9.,A process of oil conversion which includes heat treating the oil tova orize the fractions to be subjected to crac ng reaction, whileretaining a high-boiling point portion thereof, including tarryconstituents, unvaporized, passing such intermingledvapor llO and liquidinto a separating chamber wherein l the liquid portions' are retainedfor sutiicient time' to permit the evolution of the vapors, withdrawingthe vapors therefrom and quickly) superheating the same to a tempera-.cause substantial deposition of carbon, and

thenA assing the largely uncracked superheate vapors throu h a mass ofporous addened in claim 3, further sorptive material w ereby saidmaterial is maintained at the required` temperature for the' desiredcracking reaction, the superheat of the va ors being sufficient to alsomaintain themV y their contained heat at cracking temperatures whilethey are being passed through said material for a period of time longenough to effect extensive cracking, and

separating a condensate of the motor fuel type from the resultantvapors.

10. A process of oil conversion which includes heating heavy mineral oilto a temperature sufficiently high to vaporize a substantial portion ofthe oil without material cracking or decomposition while leavingunvaporized a high-boiling point portion thereof, including tarryconstituents, passing the intermingled vapor and unvaporized oil to aseparating chamber wherein the vapors are evolved from said liquid oil,withdrawing theevolved vapors and heating the same to a temperatureabove that required for the desired cracking reaction but within aperiod of time so short. that no cracking occurs sufficient to causesubstantial deposition of carbon, passing the superheated vapors througha mass of porous adsorptive contact material, said vapors beingsuperheated sufficiently to maintain by their contained heat the desiredcracking reaction of the vapors when passed through said material, andto maintain said material at the required temperature for said reaction,the duration of such passage of the4 vapors being long enough to effectextensive cracking, and separating a condensate of the motor uel typefrom the resultant vapors.

11. A process of oil conversion which includes heat-treating the oil tovaporize the fractions to be subjected to cracking while retaining ahigh-boiling portion, including tarry constituents, unvaporized, passingthe intermingled vapor and liquid oil to a separating chamber, whereinthe same is retained for the desired time for the evolution of vapors,withdrawing the vapors therefrom and superheating the same to atemperature above the temperature of the desired cracking reaction butwithin a period of time so short that no cracking occurs suil'icienttocause substantial deposition of carbon, assing the largely uncrackedsuperheate pors through a mass of porous adsorptive contact material,said vapors being superheated suiciently to maintain by their con-V,tained heat and without the input of additional heat the desiredcracking reaction of the vapors when passed through said contactmaterial and to maintain said material at the required temperature forsaid reaction, the duration of such assage 'of the vapors bein longenough to e ect extensive cracking, an separating a condensate of themotorA fuel type from the resultant vapors. 12. In a process of crackingoil in vapor phase to produce lower boiling point prod' ucts, passing amineral oil in a relatively small stream through a heating zone, whereina substantial portion of tlie-oil is vaporized without material crackingor decomposition while a higher boiling point yportion thereof,including tarry residuents, is unvaporized, discharging such vapor andliquid ,oil into a separating chamber, wherein the liquid oil isretained for suiicient time to permit the evolution and withdrawal ofthe vapors, passing the withdrawn vapors at high velocity through aheated coil, wherein they are rapidly raised to a temperatureapproximating 600 C., but within a period of time so short that nocracking occurs sufficient to cause substantial `deposition of carbon,and discharged therefrom largely uncracked and vpassed into a crackingchamber, wherein the temperature is below 600 C. but maintained by thecontained heat of said vapors suiciently high for effective cracking,retaining the vapors in said chamber a suiiicient time to insureextensive cracking, and recovering a relatively lowboiling pointcondensate from the removed cracked vapors.

13. Apparatus for converting mineral oil into lower-boiling productswhich comprises, in combination, means for heatin oil to obtain oilvapors mixed with liquid oil, mechanical separating means connected tosuch heating means and into which such vaporliquid mixture isdischarged, su erheater means arranged to receive vapor rom saidseparating means and to heat the same to cracking temperature, and aheat-insulated cracking chamber, containing a mass of porous adsorptivecontact material of the character described, connected to saidsuperheater means for receipt of vapors therefrom.

In testimony whereof I hereunto atiix my signature.

WILLIAM G. LEAMON.

